A high-quality laser polishing method based on surface micro-texture induction

Abstract

The application provides a high-quality laser polishing method based on surface micro-texture induction, comprising the following steps: setting geometric parameters of a micro-texture induction layer of a workpiece polishing surface; machining the set micro-texture induction layer on the workpiece polishing surface; ultrasonic cleaning the workpiece polishing surface with the micro-texture induction layer; placing the workpiece into a closed argon atmosphere; setting laser machining parameters and laser scanning paths according to physical properties of the workpiece metal material and the structure of the micro-texture induction layer; and performing laser polishing treatment on the workpiece polishing surface according to the laser machining parameters and the laser scanning paths. The method can make the melt flow more uniform and regular by machining the micro-texture induction layer on the polishing surface before laser polishing, and is beneficial to the improvement of the surface quality and physical properties of the workpiece after laser polishing.

Description

Technical Field

[0001] This invention relates to the field of laser polishing technology, and more specifically, to a high-quality laser polishing method based on surface microtexture-induced polishing. Background Technology

[0002] Laser thermal polishing is a surface treatment technique that uses a laser beam to apply heat to the surface of a metal workpiece. Within a very short time, a large amount of heat accumulates in the near-surface region, causing the temperature to rise rapidly. This results in the melting and solidification of the metal material, essentially removing microscopic peaks and filling valleys, to reduce the surface roughness of the workpiece. Laser thermal polishing can be divided into two categories: when the depth of the molten pool is less than the peak-valley height, it is called shallow-melt polishing; and when the depth of the molten pool is greater than the peak-valley height, it is called deep-melt polishing.

[0003] In laser shallow-melt polishing, the peaks of the rough metal surface melt first. The melt is simultaneously subjected to capillary forces along the surface normal and thermocapillary forces along the free-form surface tangentially, flowing towards the valleys. This causes the curvature to become more uniform, thus smoothing the workpiece surface and reducing roughness through "melt peak filling valley." Compared to laser surface deep-melt polishing, which generates vaporization and plasma backlash during the polishing process, laser shallow-melt polishing can achieve even lower surface roughness.

[0004] Under the action of long-pulse laser, the material surface undergoes heating, melting, and solidification to form a molten layer and a heat-affected zone with different microstructures. The grains in the molten layer can have their growth direction controlled by the temperature field and melt flow; while the grains in the heat-affected zone are affected by the "solid solution effect," which influences their grain size. Furthermore, the molten pool depth during continuous polishing with long-pulse laser can reach 100–200 μm.

[0005] However, during laser thermopolishing, the geometry of the molten pool and the flow characteristics of the melt significantly affect the surface roughness of the workpiece after polishing. For example... Figure 1 As shown, in a typical rough surface 1, the irregular distribution of peak-valley spacing, inconsistent peak-valley heights, and surface impurities lead to material irregularities. On the one hand, this results in inconsistent absorption rates of laser energy, leading to variations in the shape of the molten pool, the size of the molten layer, and the grain size of the heat-affected zone. On the other hand, it also causes both deep and shallow melting mechanisms to coexist, making the flow of the melt 2 uncontrollable. These factors make the laser shallow melting polishing process for a typical rough surface 1 poorly controllable, and may even result in inconsistent roughness and physical properties across different parts of the polished surface, which is unacceptable for some high-precision products. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a high-quality laser polishing method based on surface microtexture induction. This method first processes a microtexture induction layer on the surface to be polished before laser polishing, which can make the melt flow more uniform and regular, and is beneficial to improving the surface quality and physical properties of the workpiece after laser polishing.

[0007] To achieve the above objectives, the present invention provides a high-quality laser polishing method based on surface microtexture-induced polishing, comprising the following steps:

[0008] Step S1: Set the geometric parameters of the microtexture-inducing layer on the surface of the workpiece to be polished;

[0009] Step S2: A set micro-texture-inducing layer is processed on the surface of the workpiece to be polished;

[0010] Step S3 involves ultrasonically cleaning the workpiece surface to be polished, which has a microtexture-inducing layer.

[0011] Step S4: Place the workpiece in a sealed argon atmosphere;

[0012] Step S5: Set the laser processing parameters and laser scanning path according to the physical properties of the workpiece's metal material and the structure of the microtexture-induced layer; perform laser polishing on the workpiece surface to be polished according to the laser processing parameters and laser scanning path.

[0013] Preferably, in step S1, the geometric parameters of the microtexture-inducing layer include the shape of the protrusions, the arrangement of the protrusions, and the setting of uniform / non-uniform distribution of the protrusions; when the uniform / non-uniform distribution of the protrusions is set to uniform distribution, the geometric parameters of the microtexture-inducing layer also include the protrusion height, the protrusion width, and the protrusion spacing; when the uniform / non-uniform distribution of the protrusions is set to non-uniform distribution, the geometric parameters of the microtexture-inducing layer also include the variation law of the protrusion height, the protrusion width, and the protrusion spacing.

[0014] Preferably, the microtexture-inducing layer has an isosceles trapezoidal cross-section for its protruding shape, or a curved cross-section for its protruding shape.

[0015] Preferably, in step S5, the laser processing parameters include fixed parameters and adjustable parameters set according to the shape of the protrusions in the microtexture-induced layer; wherein, the fixed parameters include the laser spot diameter, repetition frequency, and number of scans; and the adjustable parameters include the laser output power and the laser scanning speed.

[0016] When the cross-section of the protrusion in the microtexture-induced layer is an isosceles trapezoid, the laser output power P1 and the laser scanning speed v1 are:

[0017]

[0018]

[0019] Wherein, laser output power P1 is in W; laser scanning speed v1 is in mm / s; L1 is the protrusion width in μm; L2 is the protrusion spacing in μm; H is the protrusion height in μm; ∝ is the tilt angle;

[0020] When the cross-section of the protrusions in the microtexture-induced layer is curved, the laser output power P2 and the laser scanning speed v2 are:

[0021]

[0022]

[0023] Wherein, laser output power P2 is in W; laser scanning speed v2 is in mm / s; L is the protrusion spacing in μm; H is the protrusion height in μm; and ρ is the top curvature radius in μm.

[0024] Preferably, among the fixed parameters, the laser spot diameter is 100 μm; the repetition frequency is 1000 kHz; and the number of scans is 1.

[0025] Preferably, in step S1, the arrangement of the microtexture-inducing layers is any one of a one-dimensional array, a two-dimensional array, or a ring array.

[0026] Preferably, in step S5, the laser scanning path refers to:

[0027] When the arrangement of the microtexture-inducing layers is a one-dimensional array, the laser scanning path is a unidirectional parallel line, scanning along the direction parallel to the one-dimensional array.

[0028] When the arrangement of the microtexture-inducing layers is a two-dimensional array, the laser scanning path is a unidirectional, uniform parallel line, and the scanning direction is arbitrary;

[0029] When the arrangement of the microtexture-inducing layers is a ring array, the laser scanning path is a series of concentric circles or spirals with the same center as the center of the ring array.

[0030] Preferably, in step S2, a predetermined microtexture-inducing layer is machined on the workpiece surface to be polished using a cutting method.

[0031] Preferably, when the arrangement of the microtexture-inducing layer is a one-dimensional array or a two-dimensional array, the cutting method refers to: machining microgrooves that match the microtexture-inducing layer on the back face of the milling cutter; the milling cutter uses climb milling to mill the workpiece surface to be polished, with a milling depth ≤ 0.05 mm.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] 1. The method of the present invention pre-processes a micro-texture induction layer on the surface to be polished before laser polishing, which makes the melt flow more uniform and regular, and is beneficial to improving the surface quality and physical properties of the workpiece after laser polishing.

[0034] 2. In the method of the present invention, under the action of long pulse laser, the microtexture-induced layer is a surface cutting hardening layer with regular structure. Its fused layer has a high nucleation rate and fast cooling rate, resulting in many grain boundaries and fine grains. Meanwhile, the grains in the heat-affected zone tend to be saturated due to different degrees of "solid solution effect", which makes the grain size larger than the matrix grains, thereby improving the polishing quality.

[0035] 3. In the method of the present invention, the shape and size of the micro protrusions in the microtexture-inducing layer can be set as needed, and the laser processing parameters are rationally set according to the geometric parameters of the microtexture-inducing layer. This ensures that the depth of the molten pool is less than the height of the protrusions, which can meet the requirements of shallow surface polishing. This makes the temperature field distribution of the metal surface controllable, the processing results predictable, and the processing efficiency improved.

[0036] 4. In the method of the present invention, when the microtexture inducing layer is set to a uniform distribution of protrusions, the melting and solidification state of various parts of the polished surface also exhibits a periodic uniform distribution, which is beneficial to improving the surface quality and physical properties of the workpiece after laser polishing; when the microtexture inducing layer is set to a non-uniform distribution of protrusions according to a certain pattern, the melting and solidification state of various parts of the polished surface also exhibits a certain pattern distribution, further enabling the surface roughness or friction coefficient, hardness and other physical properties to be distributed according to a certain pattern, and surfaces with special uses can be prepared.

[0037] 5. The method of the present invention has a simple microtexture-induced layer processing process. Since the micro-protrusion structure is obtained by metal cutting, it can achieve large-area or large-volume processing and has speed. The polishing process uses laser polishing, which is convenient and can achieve curved surface processing, etc., and has universality. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the polishing of rough surfaces using existing laser polishing technology;

[0039] Figure 2 This is a flowchart of the high-quality laser polishing method of the present invention;

[0040] Figure 3 This is a schematic diagram illustrating the changes in the surface to be polished using the high-quality laser polishing method of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of the microtexture-inducing layer as a one-dimensional array in the high-quality laser polishing method of the present invention;

[0042] Figure 5This is a schematic diagram of a curved surface structure in which the microtexture induction layer is a one-dimensional array in the high-quality laser polishing method of the present invention;

[0043] Figure 6 This is a schematic diagram of the structure of the microtexture induction layer as a two-dimensional array in the high-quality laser polishing method of the present invention;

[0044] Figure 7 This is a schematic diagram of the structure of the microtexture induction layer as a ring array in the high-quality laser polishing method of the present invention;

[0045] Figure 8 This is a schematic diagram of the cross-section of the microtexture-inducing layer in the high-quality laser polishing method of the present invention, which is an isosceles trapezoid.

[0046] Figure 9 This is a schematic diagram of the cross-section of the microtexture-inducing layer in the high-quality laser polishing method of the present invention, which is curved.

[0047] Figure 10 This is a cutting schematic diagram when the microtexture-inducing layer is a one-dimensional array or a two-dimensional array in the high-quality laser polishing method of the present invention;

[0048] Figure 11 This is a schematic diagram of the laser scanning path when the microtexture induction layer is a one-dimensional array in the high-quality laser polishing method of the present invention;

[0049] Figure 12 This is a schematic diagram of the laser scanning path when the microtexture induction layer is a two-dimensional array in the high-quality laser polishing method of the present invention;

[0050] Figure 13 This is a schematic diagram of the laser scanning path when the microtexture induction layer is a ring array in the high-quality laser polishing method of the present invention. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0052] Example

[0053] This embodiment presents a high-quality laser polishing method based on surface microtexture-induced processes, the flow of which is as follows: Figure 2 and Figure 3 As shown, it includes the following steps:

[0054] Step S1: Set the geometric parameters of the microtexture-inducing layer on the workpiece surface 4 to be polished.

[0055] The geometric parameters of the microtexture-inducing layer include the shape of the protrusions, their arrangement, and whether the protrusions are uniformly or non-uniformly distributed. When the protrusions are uniformly or non-uniformly distributed, the geometric parameters of the microtexture-inducing layer also include the protrusion height, protrusion width, and protrusion spacing. When the protrusions are non-uniformly or non-uniformly distributed, the geometric parameters of the microtexture-inducing layer also include the variation patterns of the protrusion height, protrusion width, and protrusion spacing.

[0056] The arrangement of the microtexture-inducing layers can be any of three types: one-dimensional array, two-dimensional array, or ring array. A one-dimensional array, such as... Figure 4 and Figure 5 As shown, Figure 5 This is a schematic diagram when the surface to be polished is curved; a two-dimensional array is shown below. Figure 6 As shown; a circular array as Figure 7 As shown. The microtexture-induced layer has a convex shape with an isosceles trapezoidal cross-section, such as... Figure 8 As shown, or the cross-section of the convex shape is curved, such as... Figure 9 As shown.

[0057] In step S2, a microtexture-inducing layer 3 is fabricated on the workpiece surface 4 to be polished. The microtexture-inducing layer 3 is a micro-protrusion structure.

[0058] Specifically, a predetermined micro-texture-inducing layer is machined onto the workpiece surface to be polished using a cutting method. For example... Figure 10 As shown, when the arrangement of the microtexture-inducing layer is a one-dimensional array or a two-dimensional array, the cutting method refers to: machining microgrooves that match the microtexture-inducing layer on the back face of the milling cutter 5; the milling cutter uses climb milling to mill the workpiece surface to be polished, with a milling depth ≤ 0.05 mm.

[0059] Step S3 involves ultrasonically cleaning the workpiece surface with the microtexture-induced layer using alcohol. This cleaning prepares the surface for subsequent polishing and improves polishing quality.

[0060] Step S4 involves placing the workpiece in a sealed argon atmosphere. The argon gas acts as an antioxidant, minimizing the negative impact of temperature on the material during polishing.

[0061] Step S5: Set the laser processing parameters and laser scanning path according to the physical properties of the workpiece's metal material and the structure of the microtexture-induced layer; perform laser polishing on the workpiece surface to be polished according to the laser processing parameters and laser scanning path.

[0062] Specifically, the laser processing parameters include fixed parameters and adjustable parameters set according to the shape of the protrusions in the microtexture-induced layer.

[0063] This invention uses long-pulse continuous laser for polishing. The selected laser processing parameters ensure that the resulting molten pool depth is less than the protrusion height (the molten pool depth is referenced to be half the protrusion height), thus satisfying the requirement of shallow-melt polishing. To achieve better polishing of surfaces with micro-texture-induced layers, the specific laser processing parameters are selected as follows:

[0064] (1) Fixed parameters include laser spot diameter, repetition frequency, and number of scans. Among the fixed parameters, the laser spot diameter is 100 μm; the repetition frequency is 1000 kHz; and the number of scans is 1.

[0065] (2) Adjustable parameters include laser output power and laser scanning speed.

[0066] When the cross-section of the protrusion in the microtexture-induced layer is an isosceles trapezoid, the laser output power P1 and the laser scanning speed v1 are:

[0067]

[0068]

[0069] Wherein, laser output power P1 is in W; laser scanning speed v1 is in mm / s; L1 is the protrusion width in μm; L2 is the protrusion spacing in μm; H is the protrusion height in μm; and ∝ is the tilt angle.

[0070] When the protrusion width L1 is 40μm, the protrusion spacing L2 is 60μm, the protrusion height H is 40μm, and the inclined angle α is 60°, the laser output power P1 is set to 100W, and the laser scanning speed v1 is set to 300mm / s. For every 5μm increase in protrusion width L1, the laser output power P1 increases by 10W, and the laser scanning speed v1 decreases by 15mm / s. For every 10μm increase in protrusion spacing L2, the laser output power P1 increases by 10W, and the laser scanning speed v1 decreases by 20mm / s. For every 10μm increase in protrusion height H, the laser output power P1 increases by 10W, and the laser scanning speed v1 remains unchanged. For every 5° increase in inclined angle α, the laser output power P1 increases by 10W, and the laser scanning speed v1 decreases by 10mm / s.

[0071] When the cross-section of the protrusions in the microtexture-induced layer is curved, the laser output power P2 and the laser scanning speed v2 are:

[0072]

[0073]

[0074] Wherein, laser output power P2 is in W; laser scanning speed v2 is in mm / s; L is the protrusion spacing in μm; H is the protrusion height in μm; and ρ is the top curvature radius in μm.

[0075] When the protrusion spacing L is 60μm, the protrusion height H is 40μm, and the top curvature radius ρ is 6μm, the laser output power P2 is set to 100W and the laser scanning speed v2 is set to 300mm / s. For every 10μm increase in protrusion spacing L, the laser output power P2 increases by 10W and the laser scanning speed v2 decreases by 20mm / s. For every 10μm increase in protrusion height H, the laser output power P2 increases by 10W and the laser scanning speed v2 remains unchanged. For every 6μm increase in top curvature radius ρ, the laser output power P2 increases by 10W and the laser scanning speed v2 decreases by 10mm / s.

[0076] The laser scanning path refers to:

[0077] When the microtexture-inducing layer 3 is arranged in a one-dimensional array, the laser scanning path 6 is a unidirectional parallel line, scanning along a direction parallel to the one-dimensional array, such as... Figure 11 As shown;

[0078] When the microtexture-inducing layer 3 is arranged in a two-dimensional array, the laser scanning path 6 is a unidirectional, uniform parallel line with arbitrary scanning direction, such as... Figure 12 As shown;

[0079] When the microtexture-inducing layer 3 is arranged in a ring array, the laser scanning path 6 is a series of concentric circles or spirals with the same center as the center of the ring array, such as... Figure 13 As shown.

[0080] The present invention has the following advantages and beneficial effects:

[0081] 1. The method of the present invention pre-processes a micro-texture induction layer 3 on the surface 4 to be polished before laser polishing, which can make the melt 2 flow more uniformly and regularly, which is beneficial to improving the surface quality and physical properties of the workpiece after laser polishing.

[0082] 2. In the method of the present invention, under the action of long pulse laser, the microtexture-induced layer 3 is a surface cutting hardening layer with regular structure. Its fused layer has a high nucleation rate and fast cooling rate, resulting in many grain boundaries and fine grains. Meanwhile, the grains in the heat-affected zone tend to be saturated due to different degrees of "solid solution effect", which makes the grain size larger than the matrix grains, thereby improving the polishing quality.

[0083] 3. In the method of the present invention, the shape and size of the micro protrusions in the microtexture-inducing layer 3 can be set as needed. The laser processing parameters are rationally set according to the geometric parameters of the microtexture-inducing layer, which can ensure that the depth of the molten pool is less than the height of the protrusion, and can meet the requirements of shallow melting and polishing of the surface, so that the temperature field distribution of the metal surface is controllable, the processing result is predictable, and the processing efficiency is improved.

[0084] 4. In the method of the present invention, when the microtexture-inducing layer 3 is set to have uniformly distributed protrusions, the melting and solidification state of various parts of the polished surface also exhibits a periodic and uniform distribution, which is beneficial to improving the surface quality and physical properties of the workpiece after laser polishing; when the microtexture-inducing layer 3 is set to have non-uniformly distributed protrusions according to a certain pattern, the melting and solidification state of various parts of the polished surface also exhibits a certain pattern, which further makes the surface roughness or friction coefficient, hardness and other physical properties distributed according to a certain pattern, and can prepare a surface with special uses;

[0085] 5. The method of the present invention has a simple processing procedure for the microtexture-induced layer 3. Since the micro-protrusion structure is obtained by metal cutting, it can achieve large-area or large-volume processing and has speed. The polishing process uses laser polishing, which is convenient to process and can achieve curved surface processing, etc., and has universality.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method of high quality laser polishing based on surface micro-texture induction, characterized by: It comprises the following steps: S1, setting the geometric parameters of the micro-texture induction layer of the workpiece surface to be polished; the geometric parameters of the micro-texture induction layer include the protrusion shape, the arrangement mode, the uniform / non-uniform distribution setting of the protrusions; when the uniform / non-uniform distribution setting of the protrusions is uniform distribution, the geometric parameters of the micro-texture induction layer further include the protrusion height, the protrusion width and the protrusion spacing; when the uniform / non-uniform distribution setting of the protrusions is non-uniform distribution, the geometric parameters of the micro-texture induction layer further include the variation law of the protrusion height, the protrusion width and the protrusion spacing; the cross section of the protrusion shape of the micro-texture induction layer is isosceles trapezoidal or the cross section of the protrusion shape is curved; S2, machining the set micro-texture induction layer on the workpiece surface to be polished by cutting for inducing melt flow; S3, ultrasonic cleaning the workpiece surface to be polished with the micro-texture induction layer; S4, placing the workpiece in a closed argon atmosphere; S5, setting the laser processing parameters and the laser scanning path according to the physical properties of the metal material of the workpiece and the structure of the micro-texture induction layer; and performing laser polishing treatment on the workpiece surface to be polished according to the laser processing parameters and the laser scanning path.

2. The method of claim 1, wherein the surface micro-texture is a plurality of micro- grooves. In the S5, the laser processing parameters include fixed parameters and adjustable parameters set according to the protrusion shape of the micro-texture induction layer; wherein the fixed parameters include the laser spot diameter, the repetition frequency and the scanning times; and the adjustable parameters include the laser output power and the laser scanning speed.

3. The high-quality laser polishing method based on surface micro-texture induction according to claim 2, wherein: when the cross section of the protrusion shape of the micro-texture induction layer is isosceles trapezoidal, the laser output power P1 and the laser scanning speed v1 are: wherein the unit of the laser output power P1 is W; the unit of the laser scanning speed v1 is mm / s; L1 is the protrusion width, unit μm; L2 is the protrusion spacing, unit μm; H is the protrusion height, unit μm; and ∝ is the inclination angle; when the cross section of the protrusion shape of the micro-texture induction layer is curved, the laser output power P2 and the laser scanning speed v2 are: wherein the unit of the laser output power P2 is W; the unit of the laser scanning speed v2 is mm / s; L is the protrusion spacing, unit μm; H is the protrusion height, unit μm; and ρ is the top radius of curvature, unit μm.

4. The method of claim 2, wherein the surface micro-texture is a plurality of micro- grooves. In the fixed parameters, the laser spot diameter is 100 μm; the repetition frequency is 1000 KHz; and the scanning times are 1.

5. The method of claim 1, wherein: In the S1, the arrangement mode of the micro-texture induction layer is any one of one-dimensional array, two-dimensional array and ring array.

6. The method of claim 5, wherein the surface micro-texture is a plurality of micro- grooves. In the S5, the laser scanning path is: when the arrangement mode of the micro-texture induction layer is one-dimensional array, the laser scanning path is a single-direction parallel line along the direction parallel to the one-dimensional array; when the arrangement mode of the micro-texture induction layer is two-dimensional array, the laser scanning path is a single-direction, uniform parallel line with an arbitrary scanning direction; when the arrangement mode of the micro-texture induction layer is ring array, the laser scanning path is a series of concentric circles or spiral lines with the same center as the ring array.

7. The method of claim 5, wherein the surface micro-texture is a plurality of micro- grooves. When the arrangement of the micro-texture inducing layer is a one-dimensional array or a two-dimensional array, the cutting method refers to: machining micro-grooves matching the micro-texture inducing layer on the rear face of a milling cutter; the milling cutter is used to mill the surface to be polished of the workpiece in a down-milling mode, and the milling depth is ≤0.05mm.

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